1. Field of the Invention
This invention is directed to insulators that retain and support electric heater coils, and to the insulators themselves.
2. Description of Related Art
Well known in the art are electric heaters that use resistance wire supported in or on a frame. Such heaters, typically called open-coil heaters, use insulators to separate the resistance wire from the frame structure and to avoid the possibility of a short circuit between the resistance wire and the frame. Such heaters use retainers to retain the wire in a predetermined configuration with respect to the frame.
Known prior art devices have attempted to provide insulators including coil holders for retaining a heater coil and insulating it from the heater framework. Wightman et al, U.S. Pat. No. 3,846,619, discloses insulators mounted on cross beams of a heater frame to support a helical heater wire. Clips attach to the insulators to support the heater coil. The clips are formed with flange surfaces bent in non-planar configurations to retain the heater wire. Insertion of part of the coil within the clip is difficult, as is removal of the coil, which might be required for maintenance or repair. The cross beams of the framework require a particular structure, and incorporate tabs to interact with portions of the insulator body to retain the insulator therein. Tabs are also required on the clips to secure them on the insulators.
Simmons, U.S. Pat. No. 1,698,282 shows an electric heater with insulators, or supports, which require special manipulation for mounting on the cross beams. Each support structure has two insulator elements. Simultaneous manipulation of the two elements is required in a 90.degree. rotation for mounting and a complicated manipulation of several combined support structures is required for the removal of a single damaged support. Cotter pins are used to secure the supports in place. The supports cannot protrude through the cross beams, i.e. they support a heater coil on only one side of the frame.
A single integral insulator for an electrical heater which is mounted to a reflector in the heater is disclosed in Hartman, U.S. Pat. No. 2,856,500. The reflector has a plurality of key openings for receiving key-like projections from the insulator. The projections are narrower than the body of the insulator, and disposed on an opposite side of the body with respect to the heater coil support means. Tabs are used in the support beams for the insulators, and special rotational manipulation is needed for mounting the insulators on the heater reflector.
A variety of U.S. Patents disclose insulators that project through a radiation panel and disclose complex insulators which have complex openings; multiple notches with coil guide surfaces; and/or external notches for support rods that at least partially encircle the insulators; see, e.g. U.S. Pat. Nos. 4,458,141; 4,617,547; 4,363,959; 4,628,190; 4,559,412; 4,268,742; 4,675,511; 4,531,017; 4,692,599; 4,481,411; 4,472,624; 4,363,959; and U.S. Pat. No. Des. 285,919.